The Mauna Loa Observatory, located on the Hawaiian islands of Mauna Loa, specializes in research in the atmospheric sciences. The facility has been collecting data on carbon dioxide levels since 1950s. The data file Maunaloa contains data on average CO2 levels (ppm) for the month of May from 1990 to 2010 (from www.esrl.noaa.gov/gmd/ccgg/trends/).
(a) Create a scatter plot of CO2 levels against year and describe the relationship.
(b) Find the equation for the least-squares equation.
(c) Plot the residuals against year. Is a straight line model appropriate? Discuss.